1. Field of the Invention
The present invention relates to ferrite cores and more particularly pertains to a new ferrite core for minimizing the circuit board footprint of a core-based component while also minimizing the total harmonic distortion exhibited by the component.
2. Description of the Prior Art
The use of ferrite cores is known in the prior art. The ferrite cores are situated in close proximity to coiled conductors to facilitate the flow of magnetic flux between the coils of a coiled conductor.
Some of the most popular prior art designs for ferrite coils are illustrated in FIGS. 1A, 1B, and 1C. These known core designs typically employ a cylindrical center leg and a horseshoe shaped outer leg. Variations include expanding the center leg along the increased gap, and placing additional breaks in the outer leg to enhance ventilation of the coiled conductor (FIG. 1B), and increasing the gap between the ends of the outer leg (FIG. 1C).
However, factors have combined to make these designs less than optimal for use in applications where circuit board space is at a premium, where the least amount of total harmonic distortion is desirable, and where interference between adjacent components should be minimized.
One area where this is especially true is in signal circuits of telecommunications applications, and one example is in the central telephone office installations of high speed telephone line service providers. The providers employ high-speed telephone line technologies such as Digital Subscriber Line (DSL), and variations of DSL such as ADSL, HDSL, SDSL, SHDSL, and MDSL, among others, for connecting customers through their conventional telephone lines to the internet and other networks. Because the provider must pay for the space occupied by the circuitry in the central telephone office, the trend has been toward miniaturization of the components mounted on the printed circuit boards of the circuits to minimize the occupied space. Miniaturization of the components not only permits more circuits, or telephone line connection ports, to be mounted on a circuit board, but also permits the circuit boards to be mounted in closer proximity to each other in a mounting rack. Thus, the trend has not only been to make the components smaller overall, but also shorter with respect to the height that the components protrude from the surface of the circuit board so that the boards can be mounted closer together in the mounting racks.
The miniaturization of the components, especially transformer and inductors and the ferrite cores employed in those transformers and inductors, has not been without its drawbacks. Smaller core sizes have required a greater number of conductor turns in the components. Increasing the number of turns in the components results in a number of detrimental effects, such as increased leakage inductance, increased distributive capacitance, increased capacitance between the primary and secondary windings of transformer components, and a general decrease in the bandwidth capacity of the components. Also, the total harmonic distortion exhibited by the newer core designs has been a concern, as well as the handling of DC bias.
In core configurations such as shown in FIGS. 1A, 1B, and 1C, the parts of the channel between the center leg and the outer leg where the width of the channel becomes larger, such as is present in these known cores below the center line (C) of the center leg, are more likely to magnetically saturate and are believed not to contribute significantly to the effective flux carrying capability of the core because the magnetic flux path length is longer than the path length in the parts of the core located above the center line (C).
The ferrite core according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing, provides an apparatus primarily developed for the purpose of minimizing the circuit board footprint of a core-based component while also minimizing the total harmonic distortion exhibited by the component.